Method and apparatus for producing double-walled containers

ABSTRACT

A method and apparatus for the formation of double-walled containers with the structure of two integrally connected and adjacent containers extending in the same direction with an air gap between them, stretch-blow moulded as single bodies out of thermoplastic material, and suitable for mass-production. A thermoplastic tubular blank is formed and then heat-conditioned. The heat-conditioned tubular blank is then mechanically stretched longitudinally and blow-formed outwards by gas pressure to conformingly and stretchingly assume the tubular blank to the shape of a first dual-container shaped mould cavity set in order to form a stretch-blow moulded first container integrally connected to a second container, with both containers extending in opposite directions. Next, additional heat-conditioning is applied to further heat-condition as necessary the stretch-blow moulded second container and if deemed an advantage, at least part of the first container. Then at least one profiled inversion piston and a second dual-container shaped mould cavity set are provided along with one or more wall stability devices applied to at least part of the wall surface(s) of either or both of the two integrally connected stretch-blow moulded containers, such that the second container side wall(s) may be inverted at least partially inside-out, while at the same time the second container bottom wall at least substantially does not invert, in order for the second container to become a substantially mirror-image inverted second container extending in the same direction as the first container, and an air gap is formed between the first container and second container.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a § 371 National Stage Entry of PCT/IB2017/056558filed Oct. 23, 2017. PCT/IB2017/056558 claims priority of NZ725552 fliedOct. 25, 2016. The entire content of these applications is incorporatedherein by reference.

FIELD OF THE INVENTION

This invention relates to a method and apparatus for the stretch-blowmoulding of double-walled containers, formed as single bodies fromthermoplastic resin tubular blanks, and which have the structure of twointegrally connected and adjacent containers extending in the samedirection and with an air gap between them, and more specifically, to amethod and apparatus suitable for high-speed mass production, producingintegral double-walled containers with very thin walls and with highlyuniform wall thicknesses.

BACKGROUND OF THE INVENTION

According to Wikipedia, a container is “a basic tool consisting of anydevice creating a partially or fully enclosed space that can be used tocontain, store, and transport objects or materials”.

As used herein, the term container refers to any receptacle of hollow orconcave inner structure that may be used to hold liquid and/or solidcontent, whether or not intended by design to hold such content, andincludes at least; a mouth opening substantially on the container radialaxis, at least one side wall disposed parallel to and/or at an angle tothe container longitudinal axis, and a bottom wall substantially on thecontainer radial axis, wherein the bottom wall may be a fully enclosedbottom wall that forms the bottom end of a fully enclosed container, ormay be a partially enclosed bottom wall that forms the bottom end of apartially enclosed container. A partially enclosed bottom wall is wherethe bottom wall surface area is substantially greater than the averageside wall surface area measured in the same radial plane. At the veryleast, a partially enclosed bottom wall may be a thickened rim sectionat the end of a side wall such as the mechanical and/or sealingconnection feature(s) on a tubular blank.

As used herein, a container may be a beaker, bottle, bowl, canteen, cap,carafe, carton, clam-shell, cover, cup, fast-food container, foodcontainer, glass, hood, lid, mug, plate, pot or tumbler, or any otherderivative of container denoting a partially or fully enclosed spacecapable of holding liquid and/or solid content.

As used herein, the term tubular denotes an object of substantiallypipe-like or tube-like form, wherein the object is hollow in nature andsubstantially cylindrical in form, however this does not by definitionmean that a tubular object is necessarily round or circular. A tubularobject may be of any cross-sectional shape or form as required for anyspecific application and/or container design, including but by no meanslimited to round, circular, ovoid, triangular, square, rectangular, orany combination of geometrical and/or non geometrical forms or shapesthereof radially and/or longitudinally.

The wording “double-walled container with the structure of twointegrally connected and adjacent containers extending in the samedirection with an air gap between them and formed as a single body” asused herein may equally be substituted with “integral double-walledcontainer”.

The wording “dual-container with the structure of two integrallyconnected containers extending in opposite directions and formed as asingle body” as used herein may equally be substituted with “integraldual-container”.

The term blow ratio as used herein may equally be substituted withexpansion ratio and denotes the ratio between any given dimensional sizeof a tubular blank (or tubular slug) prior to blow-forming and therespective dimensional size of the container once blow-formed.

The wording “mould cavity set” as used herein denotes a mould Whichtypically includes two substantially similar mould halves, however aswill be apparent to those versed in the art, this should not beconsidered as limiting a mould cavity set to only two mould components.There may be any number of integral and/or separate parts that form amould cavity set.

There are countless low cost containers made globally each year whichare suitable for mass-production. As regards low cost containersmass-produced by means of blow-forming from thermoplastic material,issues relating to low-cost production include but are by no meanslimited to:

-   -   Low cost thermoformable plastic resin,    -   Thin wall sections/light empty-weight,    -   High production speed,    -   Small production line footprint to enable small-cell production        facilities that can be located adjacent to distribution centres,        thereby minimising logistics costs,    -   Production method based on primary processes,    -   High degree of recyclability,    -   Maximising stackability to minimise logistics and storage costs,    -   Small number of subcomponent parts,    -   Small number of production processes.

Currently, almost all mass-produced containers are single walled bynature. The prime reasons are that current production processes areeither incapable of making integral double-walled containers, or anyproduction method currently utilised that may be capable of producingintegral double-walled containers results in commerciallycost-prohibitive production unit costs.

By way of example; a current method of thermoplastic cup production isby thermoforming, wherein pre-processed flat sheets of thermoplasticmaterial are heated up towards the thermoplastics resin's softeningtemperature, but usually not above the melt temperature, and then gaspressure and/or mechanical stretching is applied to heat-form the flatsheet into container-shaped mould cavities. By this method,single-walled structures are readily formable out of flat sheets,however no known variation of the thermoforming process from flat sheetscan viably create complete double-walled structures as this wouldrequire at least some of the wall structure to effectively shrink ratherthan stretch during heat-forming and this is contrary to the basis ofthe production method.

As another example, some bottle-shaped containers are produced byextrusion-blow moulding, wherein tubes of thermoplastic material thatare above their melt temperature (molten) are extruded betweencontainer-shaped mould cavity sets and then while still in a moltenstate, gas pressure is applied to heat-form the molten thermoplasticresin into the cavities. The issues relative to mass production withthis process are that molten tube extrusion is very slow and thereforehigh production speeds are not achievable, and while in the moltenstate, there is a practical limit to how thin-walled the final containercan be. Typically for this process, wall thicknesses are substantiallygreater than 1 mm, which for mass-produced containers is commerciallycost-prohibitive.

There are any number of market-driven reasons for the likes of anintegral double-walled container with the structure of two integrallyconnected and adjacent containers with an air gap between them andformed as a single body, including but not limited to:

-   -   The formation of a fully recyclable coffee cup,    -   The formation of a cold cup that does not form condensation on        outside walls,    -   The formation of a cold cup that can extend beverage shelf life,        and    -   The formation of a container that extends the period that its        contents remain hot.

Using the cup genre within the boarder container sector as an example,and other than the widely used coffee-cup solution of a separateheat-sleeve to protect a user from burning their hand, the typicalsolution a user resorts to when addressing any of these needs is theplacing of a cup inside a cup in order to form a “double-walledcontainer with an air gap”. From a mass production point of view, this“cup inside a cup” solution, as with the separate coffee-cupheat-sleeve, adds significant additional cost and leads to increasedwastage, which is counter-productive to any recycling requirement.

For mass production and across all container genres, a cost-effectivesolution lies in the ability to form a container inside of a container,structured such that the two containers are formed as a single body, andwhereby an air gap is formed between the two integral and adjacentcontainers.

BRIEF DESCRIPTION OF THE PRIOR ART

U.S. Pat. No. 3,182,842A teaches a double-walled container structureproduced by extrusion-blow moulding, with various phases of productiontaught, all of which occur while the container remains in a moltenstate. Only when the full and complete double-walled container has beenformed is the container allowed to cool sufficiently such that thethermoplastic resin is allowed to drop below its melt temperature andthereby solidify.

As already noted, extrusion-blow moulding is typified by low productionspeeds and substantially thick-walled finished products and rarely ifever has as a process been capable of producing low-cost mass-producedcontainers, however this was the main thermoplastic blow-formingmethodology of the era when this patent was filed in 1953. Over ensuingdecades, significant advances in blow-forming production methods havebeen derived that are more suitable for thin-walled structures.

U.S. Pat. No. 3,612,346 teaches a double-walled cup structure producedby thermoforming from pre-processed flat sheet, wherein a portion of theflat sheet is integrally formed into an exterior inversely tapered wallsection covering at least part of the central cup section.

While this patent primarily teaches an inversely tapered section ofexternal double-side-wall for assisting with vending machine cupstackability, the patent does show a cup with an inversely taperedexterior double-side-wall extending down past the bottom wall of thecentral cup section. As this patent is predicated on thermoforming cupsfrom pre-processed flat sheet, this cup image as shown is unlikely to beproducible as-taught as no known thermoplastic resin can heat-stretch insome areas under the application of heat and pressure (the central cupsection) while at the exact same time heat-shrink in other areas (theinversely tapered exterior wall). Even if such thermoplastic resinexisted, the inversely tapered exterior double-side-wall would not be ofuniform wall thickness as depicted, but rather would have asubstantially graduated wall thickness with the wall thicknessincreasing inversely to radial diameter decrease; as in thinner adjacentto the cup's drinking lip and thicker at the bottom edge.

In the unlikely event a method of thermoforming this cup as-taught froma flat sheet were found to be achievable, the resulting cup would becost-prohibitive as a mass-produced container since thermoforming initself cannot form ultra-thin cup walls and the graduated wall thicknessof the inversely tapered exterior double-side-wall would significantlyimpact final cup empty-weight and thereby cup unit cost. As by example,a single-walled 500 ml cup for fast-food applications formed bythermoforming has a typical wall thickness in the order of 0.35 mm and atypical cup empty-weight in the order of 13 grams. With the addition ofan integral inversely tapered exterior double-side-wall formed byshrink-forming from an initial flat sheet, likely cup empty-weight wouldbe at least double the current typical cup weight.

U.S. Pat. No. 3,969,060 teaches a method of blow moulding bottles basedon the deformation of a tubular slug of thermoplastic material. The slugis of tubular shape with only one open end and is produced in a separateinjection-moulding process. At a later time and separate to theinjection-moulding process, the tubular slug is heat-conditioned so thatits temperature is in the heat-softened range but typically well belowthe thermoplastic resin's melt temperature, and once heat-conditioned tothe desired temperature, the tubular slug is expanded outwardly undermechanical and/or gas pressure to stretchingly assume the cavityconfiguration of an external mould cavity set and thereby a finishedbottle product is formed.

This process, which was first taught in approximately 1976,revolutionised the production of thin-walled bottles. When athermoplastic resin needs to be above room temperature for heat-forming,it equally needs to be subsequently cooled back down to nearby roomtemperature post-forming and these heating and cooling times impact onoverall production speed and therefore product unit cost. Byblow-forming well below a thermoplastic resin's melt temperature,heat-up and cool-down times are significantly reduced as compared withextrusion blow-moulding, thereby overall production speed issignificantly increased. In addition, thermoplastic resins typicallystretch more uniformly when they are below their melt-temperature, soreliable production of significantly thinner-walled bottles becamepossible with the advent of this process. As an added bonus, the thinnerthe wall of the finished product, the quicker the product can be cooledback down to nearby room temperature.

With the advent of this process, known as “stretch blow-moulding”, theprocess of extrusion blow moulding all-but disappeared relative tomass-produced bottle-shaped container production.

U.S. Pat. No. 9,339,979 teaches a double-walled thermal barrier cupthermoformed as a single piece out of thermoplastic material with atleast one rib maintaining partial spacing between inner and outer walls,and with the as-formed cup having a sealed insulation space. While thecup formation process itself is not taught other than referring to“thermoforming”, the patent does show the double-walled thermal barriercup being formed from a tube with first and second open ends and beingformed by using the application of heat, pressure and an external mould,and it does teach as-formed cups having wall thicknesses of about 0.35mm.

It is well known by those versed in the art that when a heat-softened(but not molten) thermoplastic resin is blow-formed radially andlongitudinally into a mould cavity, there is a practical limit as to howfar a resin can reliably stretch under the application of gas pressure,with the practical blow ratio limit considered to be a 3 times expansionratio between the initial tubular blank prior to blow-forming and theblow-formed finished product, it is equally well known by those versedin the art that prior to blow-forming a heat-softened thermoplasticresin, it may be mechanically stretched longitudinally by typically muchmore than a 3 time ratio. It is this combination of mechanicalstretching then blow-forming of heat-softened thermoplastic resin thatis the basis of current thin walled container production.

In order to achieve very thin-walled container production, stretch-blowmoulding is typically used rather than thermoforming. The stretch-blowmoulding of a tubular blank into a blow-formed container is acombination of:

-   -   Mechanical stretching in a longitudinal direction—herein defined        as the Longitudinal Stretch ratio LS and herein calculated as        L1/L0, where L1 is the tubular blank stretched length and L0 is        the tubular blank initial length, and    -   Gas pressure stretching in a longitudinal and/or radial        direction—herein defined as the Radial Stretch ratio RS and        herein calculated as R1/R0, where R1 is the circumference at any        point after pressure stretching and R0 is the respective initial        tubular blank circumference.    -   RSmax is herein defined as the largest value of RS occurring        along the length of the tubular blank.    -   These two ratios can then herein be combined into an overall        stretch-blow mould ratio RL calculated as RS/LS, with RLmax        being the maximal RL calculable at any point along the tubular        black, herein calculated as RSmax/LS.

Primarily due to thermoplastic resin physical property constraints, ifRSmax significantly exceeds 3 then typically container rupture occursduring blow-forming, and when mechanical stretch is present, LS isalways greater than 1. Therefore, for viable blow-forming of verythin-walled containers, RLmax typically should not exceed 3.

In U.S. Pat. No. 9,339,979 there is no teaching of mechanical stretchingof the heat-softened tubular blank prior to blow-forming, so as-taughtthe LS ratio is 1. in the Figures provided, the circumference of thetubular blank (depicted by means of the tube-shaped pinch-points in thecups two bottom walls) as compared with the largest circumference in theblow-formed cup product (the transition region between the twointegrally formed cup shapes) depicts an RSmax considerably greater than3. it would therefore be obvious to those versed in the art that thedouble-cup form as taught would be at-best highly impractical toblow-form due to both RSmax and RLmax being significantly greater than3, and even if blow-formable without a high percentage rupturing, theresulting as-formed product would not have the uniform wall thicknessdepicted. While some areas such as the transition region may exhibitthin-walled properties, in all likelihood other regions such as thebottoms and adjacent side wails would be far from thin-walled in nature.

Considering alone that U.S. Pat. No. 9,339,979 describes blow-formedcups having a wall thickness of about 0.35 mm, the double-walled thermalbarrier cup as-taught would be at least twice the weight of an existingthermoformed single-walled cup of comparable volumetric capacity andtherefore would be commercially cost-prohibitive as a mass-producedcontainer.

The object of the present invention is to overcome some of thedisadvantages with the formation of integral double-walled containerswith the structure of two integrally connected and adjacent containerswith an air gap between them and formed as single bodies such that theybecome commercially viable as mass-produced thin-walled containers.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention there isprovided a method and apparatus for the production of double-walledcontainers with the structure of two integrally connected and adjacentcontainers extending in the same direction with an air gap between them,stretch-blow moulded as single bodies out of thermoplastic material, andsuitable for mass-production. Initially, a thermoplastic tubular blankwith at least one open end is formed, wherein its RSmax is substantially3 or less in order to minimise the wall thickness of both the tubularblank and of the integral double-walled container to be stretch-blowmoulded. The tubular blank is allowed to cool sufficiently such that itdrops below its melt temperature and thereby solidifies. The tubularblank is next heat-conditioned to a first heat-conditioned temperaturewithin the heat-softened temperature range but below the melttemperature of the thermoplastic material. Once heat-conditioned, thetubular blank is then mechanically stretched in a longitudinal-axisdirection with an LS substantially greater than 1, and blow-formedoutwardly by gas pressure such that RLmax is less than 3, and preferablyin the order of 1 or less. The longitudinal mechanical stretchingcombined with the longitudinal and/or radial gas pressure stretchingconformingly and stretchingly assumes the tubular blank to the shape ofa first dual-container shaped mould cavity set in order to form as anintermediate product a stretch-blow moulded integral dual-container withthe structure of a first container and integrally connected secondsmaller container, with the first container and second smaller containerextending in opposite directions from each other.

Next, further heat-conditioning is applied to heat-condition thestretch-blow moulded second smaller container and if deemed anadvantage, at least part of the first container to a secondheat-conditioned temperature. Then at least one profiled inversionpiston and a second dual-container shaped mould cavity set are providedalong with one or more wall stability devices which are applied to atleast part of the wall surface(s) of either or both of the twointegrally connected stretch-blow moulded containers, such that thesecond smaller container side wall(s) may be inverted at least partiallyinside-out, while at the same time the second smaller container bottomwall at least substantially does not invert, in order for the secondsmaller container to become a substantially mirror-image inverted secondsmaller container extending in the same direction as, and interior to,the first container. Alternately, a second smaller container may bemanually inverted.

A tubular blank may have only one open end, in which case the firstdual-container shaped mould cavity set may have at least two separatedual-container shaped mould cavity halves which may each include a firstcontainer cavity recess with a mouth opening, side wall(s) and a partialenclosed bottom wall and may all include small-radius wall-rigidityfeatures and/or at least partial air gap sealing features, and a secondsmaller container shaped cavity recess with a mouth opening, sidewall(s) and a fully enclosed bottom wall and may all includesmall-radius wall-rigidity features and/or at least partial air gapsealing features, with the two container shaped cavity recessesextending in opposite directions from each other and integrallyconnected.

A tubular blank may have a first and second open end, in which case thefirst dual-container shaped mould cavity set may instead include a firstcontainer cavity recess with a mouth opening, side wall(s) and apartially enclosed bottom wall and may all include small-radiuswall-rigidity features and/or at least partial air gap sealing features,and a second smaller container cavity recess with a mouth opening, sidewall(s) and a partially enclosed bottom wall and may all includesmall-radius wall-rigidity features and/or at least partial air gapsealing features, with the two container shaped cavity recessesextending in opposite directions from each other and integrallyconnected.

Whatever the format of the tubular blank, a second dual-container shapedmould cavity set may have two separate dual-container shaped mouldcavity halves which may each include at least one profiled inversionpiston recess, a first container cavity recess with a mouth opening,side wall(s) and a partial enclosed bottom wall and may all includesmall-radius wall-rigidity features and/or at least partial air gapsealing features, and a second smaller container shaped cavity recesswith a mouth opening, side wall(s) and a partially enclosed bottom walland may all include small-radius wall-rigidity features and/or at leastpartial air gap sealing features, with the two container shaped cavityrecesses extending in opposite directions from each other and integrallyconnected, and may include one or more devices for stretch-blow mouldedfirst and/or second smaller container heat-conditioning and may includepathways for interconnection with at least one below atmospheric airpressure source.

Due to the combination of the mechanical stretch-phase prior to theblow-phase having an LS substantially greater than 1, the tubular blankhaving an RSmax substantially 3 or less, and the second smallercontainer inversion being assisted by the wall stability device(s) andthe profiled inversion piston(s), an integral double-walled containerwhich has the structure of two integrally connected and adjacentcontainers extending in the same direction With an air gap between themmay be formed as a single body suitable for mass-production. The air gapso formed may be a partially sealed or an open air gap.

Additional production steps may be added at any sequence point,including but not limited to:

-   -   The use of the wall stability device(s) and the profiled        inversion piston(s) to stretchingly extend side-wall length of        the inverted second smaller container,    -   Cutting away any part or parts of either integrally connected        container and/or the tubular blank by any method and for any        reason,    -   Converting any partially enclosed bottom wall into a fully        enclosed bottom wall by any method and may result in a fully        enclosed air gap being formed,    -   Further inverting any features or wall sections in either        integrally connected container by any method and for any reason        and may result in a partially or fully enclosed air gap being        formed,    -   Adding an additional part or parts of any shape or form to        either integrally connected container by any method and for any        reason and may result in a partially or fully enclosed air gap        being formed,    -   Adding additional material or materials of any form, property or        nature into the air gap by any method and for any reason        including heat-insulation improvement,    -   The application of additional shaping/forming methods to ensure        that the inverted second smaller container fully assumes its        final design shape/form,    -   Printing onto any surface of either integrally connected        container by any method.

As heat-conditioned tubular blanks are stretched by mechanical and/orgas pressure devices in order to stretchingly conform them todual-container shaped mould cavity sets, at one or more locations theymust;

-   -   Be mechanically clamped sufficiently to enable them to be        mechanically stretched, and    -   Be sealingly clamped sufficiently such that gas pressure may be        applied into their interior.

All tubular blank open ends may have mechanical clamping features, andat least one tubular blank open end may have sealing damping features.Typically at least one open end of a tubular blank will be substantiallyround as this provides the most secure and efficient configuration forboth mechanical and sealing attachment. However, other than at the openend(s), a tubular blank's circumferential shape may be any combinationof geometric and/or non-geometric forms, or any change or changes incircumference, as intended by design and relative to tubular blankexpansion according to the final blow-formed container shape.

When a tubular blank is stretchingly blow moulded into a dual-containershaped cavity set, the larger the blow ratio, the more difficult it canbe to achieve uniform as-blown container wall thicknesses. As will beobvious to those versed in the art, in substantially the middle regionof a tubular blank from which the main part of a container isstretch-blow moulded, substantially uniform blow-forming is typicallyachieved and therefore fairly uniform container wall thicknesses in thiszone are readily achievable. However, in the end-zones of a tubularblank which typically form container mouth openings and bottom walls,the larger the blow ratio, or in other words the smaller the size of theinitial tubular blank with respect to the final container size, the moredifficult it can be to achieve substantially uniform wall thickness inthe matching zones of a container. Therefore, typically when the size ofthe tubular blank is substantially smaller than the final containersize, thicker wall sections result near the container mouth opening andcontainer bottom and thinner wall sections result in the middle of thecontainer.

For the production of many bottle items this is not a problem, howeverfor mass produced containers, lack of wall thickness uniformity directlytranslates into material waste and therefore commercially prohibitiveproduct unit cost.

By ensuring that tubular blanks by design have an RSmax substantially 3or less:

-   -   Tubular blanks thereby have the thinnest wall thickness possible        relative to the final container to be stretch-blow moulded,    -   Tubular blank wall thickness is thereby further reduced by means        of the mechanical stretch phase, and    -   When the stretch-blow mould phase commences, tubular blanks        stretch outwardly as uniformly as possible.

As a result of tubular blank design, the process apparatus and theproduction steps as taught herein, an integral double-walled containerwith the thinnest viable wall thickness and a high degree of wallthickness uniformity may be stretch-blow moulded, and thereby anintegral double-walled container may be formed that is highly suitablefor mass production. The intent is for the stretch-blow mould method andapparatus to achieve highly uniform average wall thicknessessignificantly less than 0.35 mm, and preferably between 0.10 and 0.30mm.

Factoring in thermoplastic resin cost and ease of recyclability, thepreferred thermoplastic resin to be used by this method and apparatus ispolypropylene (PP), however depending on the integral double-walledcontainer's specific market application, any suitable thermoplasticresin may equally be used.

A thermoplastic resin used by this method and apparatus may be oil basedor bio-based, clear/transparent, semi-transparent or opaque, of itsnatural resin colour or of any colour or combination of colours to suitan application, a single resin type or a blend of resin types, or anycombination thereof.

Tubular blank heat-conditioning to the first heat-conditionedtemperature and second heat-conditioned temperature may be:

-   -   An increase in temperature if by example tubular blanks and/or        integral dual-containers are formed remotely to any relevant        stage in an integral double-walled container forming sequence        and thereby need to be heated upwards to heat-conditioned        temperature,    -   A decrease in temperature if by example tubular blanks and/or        integral dual-containers are formed adjacent to or integral to        any relevant stage in an integral double-walled container        forming sequence and thereby need to be cooled downwards to        heat-conditioning temperature, or    -   Any combination thereof.

Preferably, the first heat-conditioned temperature is in the order of 80to 100 degrees Centigrade and the second heat-conditioned temperature isin the order of 60 to 120 degrees Centigrade. The first heat-conditionedtemperature may be the same as the second heat-conditioned temperature,or both may have different heat-conditioned temperatures.

Heat-conditioning, whether an increase in temperature or a decrease intemperature, may equally be applied to any one or more apparatus partsor sub-parts, such as by example only:

-   -   Applying cooling to one or more regions in a mould cavity set in        order to assist with returning a blow-formed integral        dual-container to substantially room temperature once a tubular        blank has conformingly and stretchingly assumed the shape of a        first dual-container shaped mould cavity set,    -   Applying cooling to a mechanical stretching device in order to        counteract mechanical stretch device heat build-up that may lead        to thin-walled tubular blank rupture during the mechanical        stretch and/or gas pressure blow-forming phases.

Gas pressure blow-forming may commence following completion oflongitudinal mechanical stretching, or gas pressure blow-forming maycommence prior to completion of longitudinal mechanical stretching.

When containers are formed with very thin walls and a high degree ofwall thickness uniformity, structural strength of the final containercan be an issue. The more geometrically simple the curved or cylindricalwall form is in a container structure, typically the lower the wallrigidity and thereby the lower the rigidity of the container, such aswith straight-sided bottle walls or conical cup walls which typicallyexhibit large-radius curves radially and are substantially linear inform longitudinally.

While thermoplastic resin selection can assist with wall rigidity,typically the more applicable thermoplastic resins for integraldouble-walled containers, such as PP, are of lower rather than higherrigidity. One way of increasing wall rigidity without impactingproduction piece cost is to introduce additional small-radius shapes orforms into finished product wall section design radially and/orlongitudinally.

As regards the second smaller container, the requirement to invert thiscontainer from its stretch-blow moulded position extending in anopposite direction to the first container into a substantiallymirror-image position interior to and extending in the same direction asthe first container preferentially requires simple large-radius walls,as such wall shapes are readily invertible (as by example, inverting aplastic contact lens), given that even when in a heat-softened state,the more complicated the geometric shape/form, the greater thedifficulty of inversion. Therefore, conical-shaped, cylindrical-shapedor high-radius compound curved cavity walls are preferred in a secondsmaller container cavity recess. While this may mean that an invertedsecond smaller container exhibits relatively low rigidity, it forms theinterior container of an integral double-walled container structure andthereby has the primary function of holding liquid/solid content, henceas with comparable container formats such as the likes of the bag in abag-in-box container, rigidity is of low importance.

As regards the first container, there is typically no requirement toinvert this container, and again as compared with comparable containerformats such as the likes of the box in a bag-in-box container, theouter container of an integral double-walled container structure has theprimary function of structural strength, therefore preferentially afirst container cavity recess may incorporate complex small-radiuscavity wall features as a way to maximise thin-walled rigidity in astretch-blow moulded integral double-walled container.

The prime purpose of an air gap between integrally connected andadjacent containers is to provide heat-insulation, both for keepingcontainer contents hot such as for coffee cups, and for keepingcontainer contents cold such as for fast-food cups and containers.However, hot and cold drinks are typically consumed relatively quickly,therefore a fully enclosed and sealed air gap is typically not necessaryfor the air gap to work effectively as a heat-insulation layer.

The term “fully enclosed” as taught in prior art presupposes that anintegral double-walled container must have two fully enclosed bottomwails, however when a container is not being held in a user's hand, itis typically standing on a substantially flat surface or held in atransit carton or tray, and as such there is typically an at leastsubstantially flat and totally separate surface underneath and directlyadjacent to the base of an integral double-walled container, therebyeffectively acting by proxy as a first container's fully enclosed bottomwall. Thus, there is typically little downside in a first containerhaving only a partially enclosed bottom wall.

While the simplest form of an integral double-walled container formed asa result of the method and apparatus taught herein results in an openair gap, there is reason to have an at least partially enclosed air gap,particularly adjacent to a first container's partially enclosed bottomwall, with reasons including overall integral double-walled containerstructural integrity and heat-insulation improvement. As alreadycharacterised, an integral double-walled container is similar to abag-in-box container format wherein the inverted second smallercontainer serves as the bag and the first container serves as the box.As an inverted second smaller container is typically thin-walled andwith little if any additional wall-rigidity features, once liquid/solidcontent is placed inside the inverted second smaller container “bag”,there is risk of it moving freely and adversely with respect to thefirst container “box”. While this movement may not lead to structuralfailure of any kind, such relative movement might at the very least beunsettling to a user.

By incorporating into a dual-container shaped mould cavity set at leastone or more complex small-radius cavity wall features in the form ofabrupt/small-radius changes extending inwards on a first containercavity recess wall(s), any movement in an inverted second smallercontainer with respect to its first container may be minimised andthereby overall structural integrity may be increased. The at least oneor more complex small-radius cavity wall features in the form ofinwardly extending abrupt/small-radius changes in a first containercavity recess wall(s) may result in a first container at least partiallyor engagingly making contact with its adjacent inverted second smallercontainer in any one or more places.

Such at least one or more complex small-radius cavity wall features inthe form of inwardly extending abrupt/small-radius curvature changes ina first container cavity recess wall(s) may also serve to provide an airgap restriction in a finished integral double-walled container in orderto provide at least partial or fully enclosed air gap sealing.

During the inversion process at least some portions of the bottom wallof a second smaller container do not necessarily need to invert,therefore a cavity recess for a second smaller container bottom wall mayalso include at least one or more complex small-radius cavity wallfeatures in the form of abrupt/small-radius curvature cavity recesschanges which may serve as a further way of reducing movement betweenadjacent integral containers in an integral double-walled containerstructure and/or as a further way of providing air gap restriction.

In order to form such advantageous wall features in a stretch-blowmoulded integral double-walled container, a dual-container mould cavityset may include, but is by no means limited to:

-   -   One or more abrupt/small-radius changes in cavity wall shape        and/or form radially and/or longitudinally or any angular        orientation in between,    -   One or more abrupt/small-radius changes in cavity wall shape        and/or form extending any distance inwards and/or outwards from        the mean surface of any cavity wall,    -   Abrupt/small-radius change in shape and/or form that are        continuous and/or discontinuous in any direction,    -   If extending inwards from a first container cavity wall, may        extend a distance by design such that the stretch-blow moulded        first container and its inverted second container when in their        final integral double-walled container structural form extending        in the same direction as each other may touchingly contact,        engagingly contact or make no contact in any one or more places,        or    -   Any combination thereof.

Examples of complex small-radius mould cavity wall features include, butare by no means limited to:

-   -   Any form of logo, graphics design, lettering, promotional        information or the like as part of a cavity wall,    -   Any geometric or non-geometric shape or form as part of a cavity        wall,    -   Any abrupt changes in cavity wall height typified by a ridge        being formed,    -   Any abrupt changes in cavity wall height that equally abruptly        returns to substantially the original cavity wall height in the        same plane typified by a cavity rib or cavity channel,    -   A raised or recessed thread form of any type as part of a cavity        wall,    -   Any combination thereof, or    -   A complex geometric cavity wall feature in the form of an        abrupt/small-radius change readily apparent to those versed in        the art.

During the stretch-blow-moulding phase, heat-conditioned tubular blankswith only one open end are outwardly expanded by mechanical and/or gaspressure such that they stretchingly conform to the shape of adual-container shaped mould cavity set. For such integral double-walledcontainers, a first dual-container shaped mould cavity set typicallyincludes integral and interconnected cavity recesses that include butare by no means limited to:

-   -   A large-aperture recess for mechanical and/or sealing        engaging-connection to the one open end of the tubular blank,    -   An engagingly connected first container cavity recess including        a mouth opening zone, side wall zone(s) and a partially enclosed        bottom wall zone that may all include small-radius cavity wall        features for any purpose,    -   An engagingly connected second smaller container cavity recess        including a mouth opening zone, side wall zone(s) and a fully        enclosed bottom wall zone that may all include small-radius        cavity wall features for any purpose,    -   With the first and second smaller container cavity recesses        extending in opposite directions from each other.

Alternately during the stretch-blow-moulding phase, heat-conditionedtubular blanks with a first and second open end are outwardly expandedby mechanical and/or gas pressure such that they stretchingly conform tothe shape of a dual-container shaped mould cavity set. For such integraldouble-walled containers, a first dual-container shaped mould cavity settypically includes integral and interconnected cavity recesses thatinclude but are by no means limited to:

-   -   A large-aperture recess for mechanical and/or sealing engaging        connection to the first open end of a tubular blank,    -   An engagingly connected first container cavity recess including        a mouth opening zone, side wall zone(s) and a partially enclosed        bottom wan zone that may all include small-radius cavity wall        features for any purpose,    -   An engagingly connected second smaller container cavity recess        including a mouth opening zone, side wall zone(s) and a        partially enclosed bottom wall zone that may all include        small-radius cavity wall features for any purpose,    -   With the first and second smaller container cavity recesses        extending in opposite directions from each other,    -   And an engagingly connected large-aperture recess for mechanical        and/or sealing engaging-connection to the second open end of a        tubular blank.

During the second smaller container inversion phase, heat-conditionedsecond smaller containers are at least partially inverted inside-out. Asecond dual-container shaped mould cavity set typically includesintegral and interconnected cavity recesses that include but are by nomeans limited to:

-   -   A large-aperture recess for mechanical and/or sealing        engaging-connection to the partially enclosed bottom wall of a        first container,    -   An engagingly connected first container cavity recess including        a mouth opening zone,    -   side wall zone(s) and a partially enclosed bottom wall zone that        may all include small-radius cavity wall features for any        purpose,    -   An engagingly connected second smaller container cavity recess        including a mouth opening zone, side wall zone(s) and a        partially enclosed bottom wall zone that may all include        small-radius cavity wall features for any purpose,    -   With the first and second smaller container cavity recesses        extending in opposite directions from each other,    -   And at least one engagingly connected profiled inversion piston        recess, which forms part of the second smaller container bottom        wall zone,    -   And may further include,    -   At least one first container and/or second smaller container        heat-conditioning device, and    -   At least one pathway for interconnection with at least one below        atmospheric air pressure source.

A second smaller container cavity recess may be slightly smaller thanits respective first container cavity recess, or a second smallercontainer cavity recess may be substantially smaller than its respectivefirst container cavity recess. A second smaller container cavity recessmay have substantially the same shape/form as its respective firstcontainer cavity recess, or a second smaller container cavity recess mayhave a substantially different or totally different shape/form to itsrespective first container cavity recess. A container-shaped mouldcavity set may be exact mirror image copies of each other, or acontainer-shaped mould cavity set may be of different cavityshapes/forms to each other.

For high speed production, it is typically preferable to have a largernumber of quick steps in a production sequence rather than a smallernumber of slow steps, as for any production sequence, overall productionthroughput is typically determined by the slowest step. It is thereforepreferable for the method and apparatus for the production of integraldouble-walled containers to include first and second dual-containershaped mould cavity sets in order to achieve the fastest possibleproduction sequence cycle-time and thereby the lowest production piececost, however as will be apparent to those versed in the art, a singledual-container shaped mould cavity set combining all features andfunctions of the two dual-container shaped mould cavity sets may equallybe used. Alternately, more than two dual-container shaped mould cavitysets may be employed in a production sequence.

In order to ensure optimal inversion of a second smaller container, itis important to control wall stability in the region where inverting andnon-inverting wall sections engagingly connect:

-   -   Where full inversion of a second smaller container into a full        mirror-image position is desired, the region for wall stability        control in a dual-container mould cavity set is the connection        region between the mouth opening zones of the first container        and second smaller container cavity recesses,    -   Where only partial inversion of a second smaller container into        a substantially mirror-image position is desired, the region for        wall stability control in a dual-container mould cavity set is        wherever deemed necessary by design with respect to the final        integral double-walled container shape to be formed.

Wherever the region for wall stability control is located within adual-container shaped mould cavity set, it is important to keep therelevant stretch-blow moulded wall region or regions as physicallystable as possible in order for a second smaller container to beinverted in an orderly manner, with the inversion process being to:

-   -   Begin with invertingly pushing with at least one profiled        inversion piston on the bottom wall of a second smaller        container such that the bottom wall remains at least        substantially non-inverted and moves first in a longitudinal        axis direction towards the mouth opening,    -   Followed by an orderly inversion of the side wall(s),        progressively starting from the bottom wall end of the side        wall(s) heading towards the mouth opening end of the side        wall(s), and    -   Finally ending with the inversion of the mouth opening or        wherever else the inversion is intended by design to conclude.

A profiled inversion piston may have any shape/form necessary to aidinversion ranging from a flat pushing face through to a fully profiledshape that conforms to the final interior inverted bottom wall shape tothereby ensure that a second smaller container bottom wall at leastsubstantially does not invert. The preferred profile is a fully profiledshape that conforms to the final interior inverted bottom wall shape.

Wall stability control devices within a dual-container mould cavity setinclude, but are not limited to:

-   -   Appling a higher than atmospheric air pressure interior to a        dual-container mould cavity set in order to provide a higher        than atmospheric air pressure interior to a stretch-blow moulded        integral dual-container during inversion,    -   Applying lower than atmospheric air pressure via a        dual-container mould cavity set to any one or more exterior        stretch-blow moulded integral dual-container wall surfaces in        the region or regions required for wall stability control,    -   Using at least one of the apertures into a dual-container mould        cavity set for the insertion of at least one flexible wall        surface support structure interior to a dual-container mould        cavity set in order to provide mechanical wall stability against        relevant interior stretch-blow moulded integral dual-container        wall surfaces and/or may have at least one head-shape so        shaped/formed in order to assist with the formation of the final        inversion shape/form desired at the point of intersection of        inverting and non-inverting walls,    -   Any combination thereof, or    -   Any other dual-container mould cavity set wall stability control        apparent to those versed in the art.

Air pressure higher than atmospheric pressure is currently used for wallstability control during wall inversion with stretch-blow-mouldedbottles, such as for the creation of integral handle-regions. However,typically the wall inversion volumetric size relative to the overallvolume of the blow-formed bottle is small and therefore any internal airpressure differential that arises as a result of wall-inversion isreadily controllable.

For integral double-walled container structures however, the differencein internal volume between the stretch-blow moulded first container andintegral second smaller container extending in opposite directions andthe final integral double-walled container where the first container andinterior inverted second smaller container extend in the same directionis substantial—and is typically more than a 10 times volumetricdifferential. Given that for high-speed production the requirement isfor inversion to occur as quickly as possible, internal air pressurebuild-up between these two vastly different internal volumes may bedifficult at best to control.

In the event that rate of change of internal air pressure can bedirectly controlled during inversion, this may be by fast-actingpneumatic control devices such as pressure regulators and/or reliefvalves. However, where rate of change in internal air pressure exceedsthe ability of fast-acting pneumatic devices to reliably control, aninversion apparatus stage may incorporate one or more separate pressurechambers that engagingly interconnect with the interior of thestretch-blow moulded first container and integral second smallercontainer such that their combined internal volume is substantiallygreater than the internal volume itself of the stretch-blow mouldedfirst container and integral second smaller container. in this way, asthe second smaller container is inverted, the substantial internalvolume change of the stretch-blow moulded integral double-walledcontainer due to inversion results in only a small overall volume changein the combined internal volume, and thereby internal air pressurechanges during inversion may be minimised and thereby readilycontrolled. Any combination of pneumatic control devices and/or one ormore pressure chambers may be used.

At least one of the apertures into a dual-container mould cavity set maybe used to insert at least one flexible surface support structureinterior to a dual-container mould cavity set in order to provideinterior wall surface stability for the stretch-blow moulded integraldouble-walled container during inversion. The one or more flexiblesurface support structures may be spring-loaded by any method in orderto springly and engagingly contact them with the relevant interior wallsurface(s) of a stretch-blow moulded integral dual container in theregions where wall surface stability is required. The one or moreflexible surface support structures may be flexibly inserted and/orflexibly withdrawn at any point prior to, during or following inversion.

The at least one flexible surface support structure interior to adual-container mould cavity set may include interior former shaping toensure that the transition region between inverting and non-invertingwalls is formed to design requirements.

While the one or more flexible surface support structures remainspringly and engagingly in contact with the interior wall surface(s) ofa now inverted integral double-walled container and by whatever method anow inverted second smaller container remains in a heat-conditionedstate, a profiled inversion piston may be further extended in theinverting direction thereby causing at least part of the bottom walland/or the side wall(s) of a now partially or fully inverted secondsmaller container to be stretchingly lengthened. By this means, theinternal volume of a now partially or fully inverted second smallercontainer may be increased while at the same time the wall thickness ofits side wall(s) is reduced. Thus, for any given target containervolumetric capacity, overall final integral double-walled containerempty-weight may be further reduced and thereby production unit costsimilarly reduced. Second smaller container wall stretching may occurafter wall inversion and/or during wall inversion. The same profiledinversion piston may be used for wall stretching, or a separate profiledpiston may be used for side wall stretching.

In the event a process step needs to be added to convert at least onepartially enclosed bottom wall into a fully enclosed bottom wall, thismay be by:

-   -   Press-fitting of additional bottom walls of any suitable        material,    -   Gluing or welding of additional bottom walls of any suitable        material,    -   Over-moulding of additional bottom walls of substantially the        same material or any material with suitable molecular bonding        properties,    -   Formation of additional bottom walls by the heat-deformation of        parts of the original tubular blank,    -   Any combination thereof, or    -   Adding additional bottom walls as apparent to those versed in        the art.

In the event a further process step needs to be added to at leastpartially or fully enclose an air gap, this may be by:

The additional inversion of any existing wall feature,

-   -   Any form of welding process,    -   Any form of gluing process,    -   The addition of any form of sealing compound,    -   The attachment of adhesive labelling,    -   Any combination thereof, or    -   Any form of additional methods for sealing readily apparent to        those versed in the art

In the event a further process step needs to be added to improve theheat-insulation properties of the air gap, this may be by the additionof any one or more insulation compounds into the air gap at any point inthe production sequence, including but not limited to;

-   -   Gaseous compounds,    -   Liquid compounds,    -   Solid compounds, or    -   Any combination thereof.

During production, a tubular blank may fully and completely be formedinto an integral double-walled container, or one or more post-processesmay be used to cut away unwanted/unused parts of a tubular blank and/orcut away any blow-formed wall parts for whatever reason in order forform a finished integral doable-walled container. As by example, themechanical and/or sealing clamp area of a tubular blank may at somepoint in a production sequence be at least substantially cut away.

A further process step may be added in order to attachingly added by anydevice or method one or more additional features, elements, walls, orsub-components to an integral double-walled container. As by exampleonly, an integral double-walled container may have a process step thatattachingly adds at any point in a production sequence the likes of:

-   -   Cup bases,    -   Cup handles,    -   Integral lid parts,    -   Glass stems,    -   Promotional items of any kind,    -   Any combination thereof, or    -   Any additional feature, element, wall, or sub-component apparent        to those versed in the art.

In the event following inversion an inverted second smaller containerdoes not fully invert into the shape/form desired, one or more furtherprocess steps may employ the use of one or more separate devices toimprove the final inverted shape/form, including but not limited to:

-   -   One or more formers of any kind,    -   The application of internal and/or external air pressure,    -   Any combination thereof, or    -   Any shape/forming correction method or device apparent to those        versed in the art.

The process steps for forming an integral double-walled container mayoccur as in-line process steps, as adjacent process steps, or as remoteprocess steps, or any combination thereof. It is preferred that theprocess steps occur in-line and/or adjacent to each other. Each processstep and apparatus device may occur once only in a production sequencein any order, or any one or more process steps and/or apparatus devicemay occur multiple times, ether sequentially of non-sequentially asrequired in order to achieve the most efficient overall productionthroughput. Anyone or more process steps as taught herein may becombined together or separated into sub-steps as required.

The prime market applications for integral double-walled containersformed as a result of the method and apparatus herein taught include,but are not limited to:

-   -   As a cup and/or lid for fast food and coffee retail outlets,    -   As a bottle or pottle for perishable foodstuffs,    -   As a bottle or pottle for pharmaceuticals, chemicals and        cosmetics,    -   As a container for fast foods,    -   As a secondary packaging cup, bottle or container for any market        sector.

In a first preferred embodiment, there is provided a method andapparatus for the production of double-walled containers with thestructure of two integrally connected and adjacent containers extendingin the same direction with an air gap between them, stretch-blow mouldedas single bodies out of thermoplastic material, and suitable formass-production. Initially, a thermoplastic tubular blank with one openend is formed, wherein its RSmax is substantially 3 or less in order tominimise the wall thickness of both the tubular blank and of theintegral double-walled container to be stretch-blow moulded. The tubularblank is allowed to cool sufficiently such that it drops below its melttemperature and thereby solidifies. The tubular blank is nextheat-conditioned to a first heat-conditioned temperature within theheat-softened temperature range but below the melt temperature of thethermoplastic material. Once heat-conditioned, the tubular blank is thenmechanically stretched in a longitudinal-axis direction with an LSsubstantially greater than 1, and blow-formed outwardly by gas pressuresuch that RLmax is less than 3, and preferably in the order of 1 orless. The longitudinal mechanical stretching combined with thelongitudinal and/or radial gas pressure stretching conformingly andstretchingly assumes the tubular blank to the shape of a firstdual-container shaped mould cavity set in order to form as anintermediate product a stretch-blow moulded integral dual-container withthe structure of a first container and integrally connected secondsmaller container, with the first container and second smaller containerextending in opposite directions from each other. Next, furtherheat-conditioning is applied to heat-condition the stretch-blow mouldedsecond smaller container and if deemed an advantage, at least part ofthe first container to a second heat-conditioned temperature. Then atleast one profiled inversion piston and a second dual-container shapedmould cavity set are provided along with one or more wall stabilitydevices which are applied to at least part of the wall surface(s) ofeither or both of the two integrally connected stretch-blow mouldedcontainers, such that the second smaller container side wall(s) may beinverted at least partially inside-out, while at the same time thesecond smaller container bottom wall at least substantially does notinvert, in order for the second smaller container to become asubstantially mirror-image inverted second smaller container extendingin the same direction as, and interior to, the first container.Alternately, a second smaller container may be manually inverted.

A first dual-container shaped mould cavity set typically includesintegral and interconnected cavity recesses that include but are by nomeans limited to:

-   -   A large-aperture recess for mechanical and/or sealing        engaging-connection to the one open end of a tubular blank,    -   An engagingly connected first container cavity recess including        a mouth opening zone, side wall zone(s) and a partially enclosed        bottom wall zone that may all include small-radius cavity wall        features for any purpose,    -   An engagingly connected second smaller container cavity recess        including a mouth opening zone, side wall zone(s) and a fully        enclosed bottom wall zone that may all include small-radius        cavity wall features for any purpose,    -   With the first and second smaller container cavity recesses        extending in opposite directions from each other.

A second dual-container shaped mould cavity set typically includesintegral and interconnected cavity recesses that include but are by nomeans limited to:

-   -   A large-aperture recess for mechanical and/or sealing        engaging-connection to the partially enclosed bottom wall of a        stretch-blow moulded first container,    -   An engagingly connected first container cavity recess including        a mouth opening zone, side wall zone(s) and a partially enclosed        bottom wall zone that may all include small-radius cavity wall        features for any purpose,    -   An engagingly connected second smaller container cavity recess        including a mouth opening zone, side wall zone(s) and a        partially enclosed bottom wall zone that may all include        small-radius cavity wall features for any purpose,    -   With the first and second smaller container cavity recesses        extending in opposite directions from each other,    -   And at least one engagingly connected profiled inversion piston        recess, which forms part of the second smaller container bottom        wall zone,    -   And may further include,    -   At least one first container and/or second smaller container        heat-conditioning device, and    -   At least one pathway for interconnection with at least one below        atmospheric air pressure source.

Due to the combination of the mechanical stretch-phase prior to theblow-phase having an LS substantially greater than 1, the tubular blankhaving an RSmax substantially 3 or less, and the second smallercontainer inversion being assisted by the wall stability device(s) andthe profiled inversion piston(s), an integral double-walled containerwhich has the structure of two integrally connected and adjacentcontainers extending in the same direction with an air gap between themmay be formed as a single body suitable for mass-production. The air gapso formed may be a partially sealed or an open air gap.

Additional production steps may be added at any sequence point,including but not limited to:

-   -   The use of the wall stability device(s) and the profiled        inversion piston(s) to stretchingly extend side-wall length of        the inverted second smaller container,    -   Cutting away any part or parts of either integrally connected        container and/or the tubular blank by any method and for any        reason,    -   Converting any partially enclosed bottom wall into a fully        enclosed bottom wall by any method and may result in a fully        enclosed air gap being formed,    -   Further inverting any features or wall sections in either        integrally connected container by any method and for any reason        and may result in a partially or fully enclosed air gap being        formed,    -   Adding an additional part or parts of any shape or form to        either integrally connected container by any method and for any        reason and may result in a partially or fully enclosed air gap        being formed,    -   Adding additional material or materials of any form, property or        nature into the air gap by any method and for any reason        including heat-insulation improvement,    -   The application of additional shaping/forming methods to ensure        that the inverted second smaller container fully assumes its        final design shape/form,    -   Printing onto any surface of either integrally connected        container by any method.

In a second preferred embodiment, there is provided a method andapparatus for the production of dual-containers with the structure oftwo integrally connected and adjacent containers extending in the samedirection with an air gap between them, stretch-blow moulded as singlebodies out of thermoplastic material, and suitable for mass-production.Initially, a thermoplastic tubular blank with a first and second openend is formed, wherein its RSmax is substantially 3 or less in order tominimise the wall thickness of both the tubular blank and of theintegral double-walled container to be stretch-blow moulded. The tubularblank is allowed to cool sufficiently such that it drops below its melttemperature and thereby solidifies. The tubular blank is nextheat-conditioned to a first heat-conditioned temperature within theheat-softened temperature range but below the melt temperature of thethermoplastic material. Once heat-conditioned, the tubular blank is thenmechanically stretched in a longitudinal-axis direction with an LSsubstantially greater than 1, and blow-formed outwardly by gas pressuresuch that RLmax is less than 3, and preferably in the order of 1 orless. The longitudinal mechanical stretching combined with thelongitudinal and/or radial gas pressure stretching conformingly andstretchingly assumes the tubular blank to the shape of a firstdual-container shaped mould cavity set in order to form as anintermediate product a stretch-blow moulded integral dual-container withthe structure of a first container and integrally connected secondsmaller container, with the first container and second smaller containerextending in opposite directions from each other. Next, furtherheat-conditioning is applied to heat-condition the stretch-blow mouldedsecond smaller container and if deemed an advantage, at least part ofthe first container to a second heat-conditioned temperature. Then atleast one profiled inversion piston and a second dual-container shapedmould cavity set are provided along with one or more wall stabilitydevices which are applied to at least part of the wall surface(s) ofeither or both of the two integrally connected stretch-blow mouldedcontainers, such that the second smaller container side wall(s) may beinverted at least partially inside-out, while at the same time thesecond smaller container bottom wall at least substantially does notinvert, in order for the second smaller container to become asubstantially mirror-image inverted second smaller container extendingin the same direction as, and interior to, the first container.Alternately, a second smaller container may be manually inverted.

A first dual-container shaped mould cavity set typically includesintegral and interconnected cavity recesses that include but are by nomeans limited to:

-   -   A large-aperture recess for mechanical and/or sealing        engaging-connection to the first open end of a tubular blank,    -   An engagingly connected first container cavity recess including        a mouth opening zone, side wall zone(s) and a partially enclosed        bottom wall zone that may all include small-radius cavity wall        features for any purpose,    -   An engagingly connected second smaller container cavity recess        including a mouth opening zone, side wall zone(s) and a        partially enclosed bottom wall zone that may all include        small-radius cavity wall features for any purpose,    -   With the first and second smaller container cavity recesses        extending in opposite directions from each other,    -   And an engagingly connected large-aperture recess for mechanical        and/or sealing engaging-connection to the second open end of a        tubular blank.

A second dual-container shaped mould cavity set typically includesintegral and interconnected cavity recesses that include but are by nomeans limited to:

-   -   A large-aperture recess for mechanical and/or sealing        engaging-connection to the partially enclosed bottom wall of a        stretch-blow moulded first container,    -   An engagingly connected first container cavity recess including        a mouth opening zone, side wall zone(s) and a partially enclosed        bottom wall zone that may all include small-radius cavity wall        features for any purpose,    -   An engagingly connected second smaller container cavity recess        including a mouth opening zone, side wall zone(s) and a        partially enclosed bottom wall zone that may all include        small-radius cavity wall features for any purpose,    -   With the first and second smaller container cavity recesses        extending in opposite directions from each other,    -   And at least one engagingly connected profiled inversion piston        recess, which forms part of the second smaller container bottom        wall zone,    -   And may further include,    -   At least one first container and/or second smaller container        heat-conditioning device, and    -   At least one pathway for interconnection with at least one below        atmospheric air pressure source.

Due to the combination of the mechanical stretch-phase prior to theblow-phase having an LS substantially greater than 1, the tubular blankhaving an RSmax substantially 3 or less, and the second smallercontainer inversion being assisted by the wall stability device(s) andthe profiled inversion piston(s), an integral double-walled containerwhich has the structure of two integrally connected and adjacentcontainers extending in the same direction with an air gap between themmay be formed as a single body suitable for mass-production. The air gapso formed may be a partially sealed or an open air gap.

Additional production steps may be added at any sequence point,including but not limited to:

-   -   The use of the wall stability device(s) and the profiled        inversion piston(s) to stretchingly extend side-wall length of        the inverted second smaller container,    -   Cutting away any part or parts of either integrally connected        container and/or the tubular blank by any method and for any        reason,    -   Converting any partially enclosed bottom wall into a fully        enclosed bottom wall by any method and may result in a fully        enclosed air gap being formed,    -   Further inverting any features or wall sections in either        integrally connected container by any method and for any reason        and may result in a partially or fully enclosed air gap being        formed,    -   Adding an additional part or parts of any shape or form to        either integrally connected container by any method and for any        reason and may result in a partially or fully enclosed aft gap        being formed,    -   Adding additional material or materials of any form, property or        nature into the air gap by any method and for any reason        including heat-insulation improvement,    -   The application of additional shaping/forming methods to ensure        that the inverted second smaller container fully assumes its        final design shape/form,    -   Printing onto any surface of either integrally connected        container by any method.

Where reference has been made to methods and/or apparatus as part of theformation of a double-walled container with the structure of twointegrally connected and adjacent containers extending in the samedirection with an air gap between them and formed as a single body froma tubular blank with only one open end, they may equally be part of themethods and/or apparatus in the formation of a double-walled containerwith the structure of two integrally connected and adjacent containersextending in the same direction with an air gap, between them and formedas a single body from a tubular blank with a first and second open end,and vice versa.

Where reference has been made to a method and apparatus that at leastsubstantially inverts the second smaller container and does not invertthe first container, equally a method and apparatus may at leastsubstantially invert the first container and may not invert the secondsmaller container.

Where reference has been made to a method and apparatus wherein thesecond container is smaller than the first container, equally a methodand apparatus may have a first container that is smaller than the secondcontainer.

Further aspects of the invention, which should be considered in all itsnovel aspects, will become apparent from the following description,which is given by way of example only.

BRIEF DESCRIPTION OF DRAWINGS

Examples of the invention will become apparent from the followingdescription which is given by way of example with reference to theaccompanying drawings which:

FIG. 1 shows a three-dimensional cross-section view of a thermoplasticresin tubular blank according to a first preferred embodiment of thepresent invention;

FIG. 2 shows a three-dimensional view of at least part of a firstdual-container shaped mould cavity set according to the same firstpreferred embodiment of the present invention;

FIG. 3 shows a three-dimensional view of at least part of a seconddual-container shaped mould cavity set according to any preferredembodiment of the present invention;

FIG. 4 shows a three-dimensional cross-section view of a profiledinversion piston according to any preferred embodiment of the presentinvention;

FIG. 5 shows three-dimensional views of alternate internal volumeconfigurations as part of higher than atmospheric air pressure interiorwall stability control according to any preferred embodiment of thepresent invention;

FIG. 6 shows a three-dimensional view of an interior flexible surfacesupport structure according to any preferred embodiment of the presentinvention;

FIG. 7 shows a three-dimensional cross-section view of a stretch-blowmoulding third step hi a sequence of production of an integraldouble-walled container according to a first preferred embodiment of thepresent invention;

FIG. 8 shows a three-dimensional cross-section view of an inversion workstation with stability control devices for stretch-blow moulded integralfirst and second smaller containers extending in opposite directionsaccording to any preferred embodiment of the present invention;

FIG. 9 shows a three-dimensional cross-section view of a first phase ofa fourth inversion step in a sequence of production of an integraldouble-walled container according to any preferred embodiment of thepresent invention;

FIG. 10 shows a three-dimensional cross-section view of a second phaseof the fourth inversion step of Fig, 9 according to any preferredembodiment of the present invention;

FIG. 11 shows a three-dimensional cross-section view of a thirdinverting phase of the fourth inversion step of FIGS. 9 and 10 accordingto any preferred embodiment of the present invention;

FIG. 12 shows a three-dimensional cross-section view of a final phase ofthe fourth inversion step of FIGS. 9 through 11 according to anypreferred embodiment of the present invention;

FIG. 13 shows a three-dimensional cross-section view of a thermoplasticresin tubular blank according to a second preferred embodiment of thepresent invention;

FIG. 14 shows a three-dimensional view of at least part of a firstdual-container shaped mould cavity arrangement according to the samesecond preferred embodiment of the present invention; and

FIG. 15 shows three-dimensional cross section views of alternatedual-container shaped mould cavity configurations according to anypreferred embodiment of the present invention.

DETAILED DESCRIPTION

It will be appreciated that terminology such as “upwards”, “downwards”etc. as used in this specification refer to the orientations shown inthe drawings and orientations obvious to those versed in the art. Theterms are used to indicate relative orientations, but should not beconsidered to be otherwise limiting.

Referring to FIG. 1, an enclosed thermoplastic resin tubular blank isdepicted in three-dimensional cross-section view according to a firstpreferred embodiment of the present invention.

According to the first preferred embodiment of the present invention, anenclosed tubular blank 1 may have only one open end 2, and may beoptimised by design such that its RSmax is substantially 3 or less inorder to minimise the wall thickness 3 of the enclosed tubular blank 1as well as to minimise the wall thickness of the integral dual-containerto be stretch-blow moulded (not depicted).

As heat-conditioned tubular blanks are stretched by mechanical and/orgas pressure in order to stretchingly conform them to dual-containershaped mould cavity sets, at one or more locations tubular blanks mustbe;

-   -   Mechanically clamped sufficiently to enable them to be        stretched, and    -   Sealingly clamped sufficiently such that pressure may be applied        into their interior.

It is typical that the open end 2 of an enclosed tubular blank 1 besubstantially round (as depicted) as this provides the most secure andefficient manner of mechanical and sealing attachment. However, otherthan at the one open end 2, the circumferential shape 4 may be anycombinational geometric and/or non-geometric forms, or any change orchanges in circumference, as intended by design and relative to tubularblank expansion according to the final double-walled container shape tobe formed.

For an enclosed tubular blank 1, mechanical damping may be effected atthe one open end ., Mechanical damping may be in the form of one or moreintegral mechanical clamping features at the one open end 2 whichengagingly interconnect with external mechanical vice or damp stylearrangements in a dual-container shaped mould cavity arrangement (notdepicted). Such rim shaped mechanical clamping features 5 maysubsequently form the partially enclosed bottom wall of a stretch-blowmoulded first container (not depicted).

For an enclosed tubular blank 1, sealing clamping may also be effectedat the one open end 2 in order for gas pressure to have at least asubstantially sealed pathway 6 into its interior and which engaginglyinterconnects with external sealing style arrangements in adual-container shaped mould cavity arrangement (not depicted). Sealingclamping is typically incorporated as part of mechanical clampingfeatures 5 at the one open end 2, and may include any combination ofcommon and/or additional integral features in order to assist withsealing.

The preferred thermoplastic resin for an enclosed tubular blank 1 ispolypropylene (PP), however any suitable thermoplastic resin may equallybe used. A thermoplastic resin may be oil based or bio-based,clear/transparent, semi-transparent or opaque, of its natural resincolour or of any colour or combination of colours, of a single resintype or of a combination of resin types, or any combination thereof.

Referring to FIG. 2, at least part of a first dual-container shapedmould cavity set k depicted in three-dimensional view according to thesame first preferred embodiment of the present invention.

According to the first preferred embodiment of the present invention, atleast part of a first dual-container shaped mould cavity set 7 typicallyincludes integral and interconnected cavity recesses that include butare by no means limited to:

-   -   A large-aperture recess for mechanical and/or sealing        engaging-connection 8 to the one open end 2 of a tubular blank 1        (not depicted),    -   An engagingly connected first container cavity recess 9        including a mouth opening zone 10, side wall zone(s) 11 and a        partially enclosed bottom wall zone 12 that may ail include        small-radius cavity wall features for any purpose, and where at        the very least a partially enclosed bottom wall may be the        mechanical and/or sealing engaging-connection features 8 at the        end of the side wall(s) 11,    -   An engagingly connected second smaller container cavity recess        13 including a mouth opening zone 14, side wall zone(s) 15 and a        fully enclosed bottom wall zone 16 that may all include        small-radius cavity wall features for any purpose,    -   With the first 9 and second smaller container 13 cavity recesses        extending in opposite directions from each other and integrally        connected 17.

Examples of complex small-radius mould cavity wall features include, butare by no means limited to:

-   -   Any form of logo, graphics design, lettering, promotional        information or the like 18 as part of a cavity wall,    -   Any geometric or non-geometric shape or form as part of a cavity        wall (not depicted),    -   Any abrupt changes in cavity wall height 19 typified by a ridge        being formed,    -   Any abrupt changes in cavity wall height that equally abruptly        returns to substantially the original cavity wall height in the        same plane 20 typified by a cavity rib or cavity channel,    -   A raised or recessed thread form of any type as part of a cavity        wall (not depicted),    -   Any combination thereof, or    -   A complex geometric cavity wall feature in the form of an        abrupt/small-radius change readily apparent to those versed in        the art.

Referring to FIG. 3, at least part of a second dual-container shapedmould cavity set is depicted in three-dimensional view according to anypreferred embodiment of the present invention.

According to any preferred embodiment of the present invention, at leastpart of a second dual-container shaped mould cavity set 21 typicallyincludes integral and interconnected cavity recesses that include butare by no means limited to:

-   -   A large-aperture recess for mechanical and/or sealing        engaging-connection 22 to the partially enclosed bottom wall of        a stretch-blow moulded first container (not depicted),    -   An engagingly connected stretch-blow moulded first container        cavity recess 23 including a mouth opening zone 24, side wall        zones) 25 and a partially enclosed bottom wall zone 26 that may        all include small-radius cavity wall features for any purpose,        and where at the very least a partially enclosed bottom wall may        be the mechanical and/or sealing engaging-connection features 22        at the end of the side wall(s) 25,    -   An engagingly connected stretch-blow moulded second smaller        container cavity recess 27 including a mouth opening zone 28,        side wall zone(s) 29 and at least part of a partially or fully        enclosed bottom wall zone 30 that may all include small-radius        cavity wall features for any purpose,    -   With the stretch-blow moulded first container 23 and        stretch-blow moulded second smaller container 27 cavity recesses        extending in opposite directions from each other and integrally        connected 31,    -   And at least one engagingly connected profiled inversion piston        recess 32 as part of the bottom wall 30 of the stretch-blow        moulded second smaller container 27,    -   And may further include,    -   At least one stretch-blow moulded first container 23 and/or        stretch-blow moulded second smaller container 27        heat-conditioning device, as depicted in the form of at least        one separate heater insert 33 with an air gap 34 between heated        and unheated areas such that the cavity heater insert 33 zone(s)        may be heated by any known method, and/or parts of the cavity        may remain unheated as desired, and    -   At least one pathway 35 for interconnection with at least one        below atmospheric air pressure source (not depicted).

Referring to FIG. 4, a profiled inversion piston is depicted inthree-dimensional cross-section view according to any preferredembodiment of the present invention.

According to any preferred embodiment of the present invention, aprofiled inversion piston 36 may have any shape/form necessary to aidinversion, ranging from a fiat pushing face (not depicted) through to afully profiled shape that conforms to the final interior inverted bottomwall shape 37 to thereby ensure that a stretch-blow moulded secondsmaller container bottom wall at least substantially does not invert(not depicted). The preferred profile is a fully profiled shape thatconforms to the final interior inverted bottom wall shape 37 andsufficiently supports a stretch blow moulded second smaller containerbottom wall during the inversion process.

As depicted, the profiled inversion piston 36 may have a recessed thread38 as one possible way of attaching a profiled inversion piston 36 to awall inverting drive mechanism (not depicted). There may be any numberof profiled inversion pistons 36 of any one or more different shape/formin a production sequence. Preferable for overall simplicity andefficiently, there is only one profiled inversion piston 36.

Wall stability control devices within a dual-container mould cavity setinclude, but are not limited to:

-   -   Applying lower than atmospheric air pressure via a        dual-container mould cavity set to any one or more exterior        stretch-blow moulded container wall surfaces in the region or        regions required for wall stability control, as depicted in FIG.        3 by the at least one pathway 35 for interconnection with at        least one below atmospheric air pressure source,    -   Appling a higher than atmospheric air pressure interior to a        dual-container mould cavity set in order to provide a higher        than atmospheric air pressure interior to stretch blow moulded        containers during inversion (not depicted),    -   Using at least one of the mechanical and/or sealing        engaging-connection feature 22 apertures in a second        dual-container mould cavity set 21 for the insertion of at least        one flexible wall surface support structure interior to a second        dual-container mould cavity set in order to provide mechanical        wall stability against relevant interior stretch-blow moulded        container wall surfaces and/or to provide at least one        head-shape so shaped/formed in order to assist with the        formation of the final inversion shape/form desired at the point        of intersection of inverting and non-inverting walls (not        depicted),    -   Any combination thereof, or    -   Any other dual-container mould cavity set wall stability control        apparent to those versed in the art.

Referring to FIG. 5, alternate internal volume configurations as part ofhigher than atmospheric air pressure interior wall stability control aredepicted in three-dimensional view according to any preferred embodimentof the present invention.

For integral double-walled container structures, the difference ininternal volume between the stretch-blow moulded first container andintegral second smaller container extending in opposite directions 39(the air volume inside the two stretch-blow moulded containers) and thefinal integral double-walled container where the stretch-blow mouldedfirst container and interior inverted second smaller container extend inthe same direction 40 (the air gap between the two stretch-blow mouldedcontainers) is substantial—and is typically more than a 10 timesvolumetric differential. Given that for high-speed production therequirement is for inversion to occur as quickly as possible, internalaft pressure build-up between these two vastly different internalvolumes may be difficult at best to control.

In the event that rate of change of internal air pressure may bedirectly controlled during inversion, this may be by fast-actingpneumatic control devices such as pressure regulators and/or reliefvalves (not depicted). However, where rate of change in internal airpressure exceeds the ability of fast-acting pneumatic devices toreliably control, an inversion apparatus stage may incorporate one ormore separate pressure chambers 41 that engagingly interconnect with theinteriors of the stretch-blow moulded first container 39 and integralsecond smaller container 40 such that theft combined internal volumes 42(=39+41) and 43 (=40+41) are substantially greater than the individualinternal volumes of the stretch-blow moulded first container 39 andintegral second smaller container 40. In this way, as the stretch-blowmoulded second smaller container is inverted from the combined internalvolume 42 into the combined internal volume 43, combined internal volumechange due to inversion is small and thereby internal air pressurechange may be minimised and readily controlled. Any combination ofpneumatic control devices and/or one or more pressure chambers 41 may beused.

Referring to FIG. 6, an interior flexible surface support structure isdepicted in three-dimensional view according to any preferred embodimentof the present invention.

According to any preferred embodiment of the present invention, at leastone large-aperture recess for mechanical and/or sealingengaging-connection 22 in a second dual-container shaped mould cavityset 21 of FIG. 3 may be used to insert at least one interior flexiblesurface support structure 44 interior to a second dual-container mouldcavity set 21 in order to provide interior wall surface stability forany stretch-blow moulded container (not depicted) during inversion. Theone or more interior flexible surface support structures 44 may bespring-loaded by any method in order to springly and engagingly contactthem with relevant interior stretch-blow moulded container wallsurface(s) in any internal surface region where wall surface stabilityis required.

As depicted, an interior flexible surface support structure 44 may haveat least one spring arm 45, and any spring arm 45 may have a shaped head46, with the head-shape so shaped/formed in order to assist with theformation of the final inversion shape/form desired at the point ofintersection of inverting and non-inverting walls. Additional springsmay be inserted at any position on an interior flexible surface supportstructure 44 (not depicted), and may advantageously be inserted betweeneach shaped head 46 in the inter-head gap 47. The one or more interiorflexible surface support structures 44 may be flexibly inserted and/orflexibly withdrawn at any point in a production sequence, whether priorto, during or following inversion.

A first step in a sequence of production of an integral double-walledcontainer may be the formation of a tubular blank 1 of FIG. 1. Followingtheir production, tubular blanks 1 are allowed to cool sufficiently suchthat they drop below their melt temperature and thereby solidify.Tubular blanks 1 may be formed integrally with or adjacent to any one ormore other sequence steps, or alternately they may be formed remotely toany one or more sequence steps. The method of formation may be by anysuitable process known to those versed in the art, but preferably is byeither injection moulding or extrusion.

A second step in a sequence of production of an integral double-walledcontainer may be the heat-conditioning of the tubular blank 1 to a firstheat-conditioned temperature. Heat-conditioning may be by any method ofheat-conditioning known to those versed in the art, and may be integralto at least one other sequence step or a separate and individualsequence step. Heat-conditioning may be an increase in temperature if byexample tubular blanks 1 are formed remotely to integral double-walledcontainer forming and thereby need to be heated upwards to heat-formingtemperature, or heat-conditioning may be a decrease in temperature if byexample tubular blanks 1 are formed adjacent to or integral to at leastone integral double-walled container forming sequence step and therebyneed to be cooled downwards to heat-forming temperature. Preferably,tubular blank 1 average heat-conditioned temperature is in the order of80 to 100 degrees Centigrade.

Referring, to FIG. 7, a stretch-blow moulding third step in a sequenceof production of an integral double-walled container is depicted inthree-dimensional cross-section view according to the same firstpreferred embodiment of the present invention.

According to the first preferred embodiment of the present invention, athird step in a sequence of production of an integral double-walledcontainer may be the stretch-blow moulding 4 of a heat-conditionedtubular blank 1. As depicted in 48 a, the heat-conditioned tubular blank1 is loaded into a first dual-container shaped mould cavity set 7. Asdepicted in 48 b, a device 49 then mechanically stretches theheat-conditioned tubular blank 1, assisted by mechanical and/or sealingfeatures 50 which may include the integral mechanical clamping features5 of the tubular blank 1 of FIG. 1 and the mechanical and/or sealingengaging-connection 8 of the first dual-container shaped mould cavityset 7 of FIG. 2. As depicted in 48 c, gas pressure (not depicted) isthen applied internally to the mechanically stretched tubular blank 1through the substantially sealed pathway 6, assisted by the mechanicaland/or sealing features 50.

The combination of mechanical stretching and gas pressure stretchingconforms the heat-conditioned tubular blank 1 to the shape of the firstdual-container shaped mould cavity set 7 to thereby form a stretch-blowmoulded integral dual-container 51 with the structure of a stretch-blowmoulded first container 52 and integrally connected second smallercontainer 53, with the first container 52 and second smaller container53 extending in opposite directions from each other.

The mechanically stretching of the heat-conditioned tubular blank 1 in alongitudinal axis direction has an LS greater than 1, and when combinedwith the blow-forming RS ratio at any point along the tubular blank,RLmax should not be substantially greater than 3 and preferably shouldbe substantially 1 or less.

Gas pressure blow-forming may commence following completion ofmechanical stretching, or gas pressure blow-forming may commence priorto completion of mechanical stretching. Heat-conditioning may occurseparately from the first dual-container shaped mould cavity set 7and/or may occur as an integral part of the first dual-container shapedmould cavity set 7 (not depicted).

Heat-conditioning, whether an increase in temperature or a decrease intemperature, may equally be applied to any one or more apparatus partsor sub-parts, such as by example only:

-   -   Applying cooling to one or more regions in a mould cavity set 7        in order to assist with returning a blow-formed integral        dual-container 51 to substantially room temperature once a        tubular blank 1 has conformingly and stretchingly assumed the        shape of a first dual-container shaped mould cavity set 7,    -   Applying cooling (not depicted) to a mechanical stretching        device 49 in order to counteract mechanical stretch device 49        heat build-up that may lead to rupture of a thin-walled tubular        blank 1 during the mechanical stretch phase 48 b and/or gas        pressure blow-forming phase 48 c.

Referring to FIG. 8, an inversion work station with stability controldevices for stretch-blow moulded integral first and second smallercontainers extending in opposite directions is depicted inthree-dimensional cross-section view according to any preferredembodiment of the present invention.

According to any preferred embodiment of the present invention, aninversion work station 54 may include any one or more of the following:

-   -   A second dual-container mould cavity set 21 (substantially one        half of the set depicted),    -   At least one method of stretch-blow moulded first container        and/or second smaller container heating, depicted as at least        one separate heater insert 33,    -   At least one pathway 35 for interconnection with at least one        below atmospheric air pressure source (not depicted),    -   At least one profiled inversion piston 36,    -   Method of movement 55 of the at least one profiled inversion        piston 36 relative to the longitudinal axis of the second        dual-container mould cavity set 21,    -   At least one interior flexible surface support structure 44, as        depicted in a springly compressed state as a result of a        spring-tensioner plate 56 in order to enable the interior        flexible surface support structure 44 to smoothly and freely be        retracted out of the interior of and/or pass into the interior        of the second dual-container mould cavity set 21 through the        large-aperture recess for mechanical and/or sealing        engaging-connection 22,    -   Method of movement 57 of the spring-tensioner plate 56        longitudinally relative to the at least one interior flexible        surface support structure 44,    -   A structure for mounting and movement support 58 of the at least        one interior flexible surface support structure 44,    -   Method of movement 59 of the structure for mounting and movement        support 58 relative to the longitudinal axis of the second        dual-container mould cavity set 21,    -   At least one integral pressure chamber 60,    -   And at least one pneumatic control device (not depicted).

Referring to FIG. 9, a first phase of a fourth inversion step in asequence of production of an integral double-walled container isdepicted in three-dimensional cross-section view according to anypreferred embodiment of the present invention.

According to any preferred embodiment of the present invention, aninversion step commences with the placement of a stretch-blow mouldedintegral dual-container 51 with the structure of a first container 52and integrally connected second smaller container 53 extending inopposite directions from each other inside of the second dual-containermould cavity set 21 of an inversion work station 54. The stretch-blowmoulded integral dual-container 51 may be of any preferred embodimentaccording to the present invention.

The at least one or more parts of a stretch-blow moulded integraldual-container 51 to be inverted need to be heat conditioned to a secondheat-conditioned temperature. Heat-conditioning may be effected by anymethod, and may occur prior to placement inside of the inversion workstation 54 and/or following placement inside of the inversion workstation 54. As depicted, the inversion work station 54 may include atleast one heater insert 33.

The second head-conditioned temperature may be the same as or differentto the first heat-conditioned temperature.

Following the placement of a stretch-blow moulded integraldual-container 51 inside of the inversion work station 54, the structurefor mounting and movement support 58 may be moved longitudinally towardsthe second dual-container mould cavity set 21, thereby moving the atleast one interior flexible surface support structure 44 interior to thestretch-blow moulded integral dual-container 51. Interior insertion ofthe at least one interior flexible surface support structure 44 may beassisted by the spring-tensioner plate 56 springly compressing the atleast one interior flexible surface support structure 44 such that itmay smoothly and freely move into the interior of the stretch-blowmoulded integral dual-container 51 through the large-aperture recess formechanical and/or sealing engaging-connection 22.

Referring to FIG. 10, a second phase of the fourth inversion step ofdig. 9 is depicted in three-dimensional cross-section view according toany preferred embodiment of the present invention.

According to any preferred embodiment of the present invention, once theat least one interior flexible surface support structure 44 has beencorrectly positioned interior to the stretch-blow moulded integraldual-container 51, the spring-tensioner plate 56 may be withdrawnbackwards with respect to the stretch-blow moulded integraldual-container 51 such that the interior flexible surface supportstructure 44 may springingly flex outwards 61 to engaginglyconnect/contact with any one or more relevant interior surfaces of thestretch-blow moulded integral dual-container 51 that may requireinversion support.

At least one pressure source (not depicted) may apply higher thanatmosphere pressure 62 interior to the combined stretch-blow mouldedintegral dual-container 51 and pressure chamber 60.

At least one pressure source (not depicted) may apply lower thanatmospheric pressure to the exterior of the stretch-blow mouldedintegral dual-container 51 in any one or more relevant places (notdepicted).

Referring to FIG. 11, a third inverting phase of the fourth inversionstep of FIGS. 9 and 10 is depicted in three-dimensional cross-sectionview according to any preferred embodiment of the present invention.

According to any preferred embodiment of the present invention, once anyone or more relevant zones of the stretch-blow moulded integraldual-container 51 have been heat-conditioned to a secondheat-conditioned temperature and any one or more methods of wallstability control have been applied, at least one profiled inversionpiston 36 may be moved longitudinally 63 with respect to thestretch-blow moulded integral dual-container 51 in order to commencestretch-blow moulded second smaller container 53 inversion.

In order to ensure optimal inversion of a stretch-blow moulded secondsmaller container 53, it is important to control wall stability in theregion where inverting and noninverting wall sections engaginglyconnect:

-   -   Where full inversion of a stretch-blow moulded second smaller        container 53 into a full mirror-image position is desired, the        region for wall stability control in a dual-container mould        cavity set 21 is the connection region between the mouth opening        zones 64 of the stretch-blow moulded first container 52 and        second smaller container 53,    -   Where only partial inversion of a stretch-blow moulded second        smaller container 53 into a substantially mirror-image position        is desired, the region for wall stability control in a        dual-container mould cavity set 21 is wherever deemed necessary        by design with respect to the final integral double-walled        container shape being formed.

Wherever the region for wall stability control is located within adual-container shaped mould cavity set 21, it is important to keep therelevant stretch-blow moulded wall region(s) as physically stable aspossible in order for a stretch-blow moulded second smaller container 53to be inverted in an orderly manner, with the inversion process beingto:

-   -   Begin with invertingly pushing with at least one profiled        inversion piston 36 on the bottom wall 65 of a second smaller        container 53 such that the bottom wall 65 remains at least        substantially non-inverted and moves first in a longitudinal        axis direction 63 towards the mouth opening 64,    -   Followed by an orderly inversion of the side wall(s) 66,        progressively starting from the bottom wall end of the side        wall(s) heading towards the mouth opening end 64 of the side        wall(s) 67, and    -   Finally ending with the inversion of the mouth opening 64 or        wherever else the inversion is intended by design to conclude.

The least one interior flexible surface support structure 44 may have atleast one head-shape so shaped/formed in order to assist with theformation of the final inversion shape/form desired at the point ofintersection of inverting and non-inverting walls, as by example onlydepicted as the mouth opening zones 64.

Any one or more methods of wall stability control may be operational atany given point within an inversion sequence, including but not limitedto:

-   -   At least one interior flexible surface support structure 44        being engaged or retracted at any point in the sequence such        that, as required, it is springly flexed outwards 61 to thereby        engagingly connect/contact with any one or more relevant        interior surfaces of the stretch-blow moulded integral        dual-container 51,    -   Above atmospheric pressure 62 applied or disengaged at any point        in the sequence,    -   Below atmospheric pressure (not depicted) applied or disengaged        at any point in the sequence, or    -   Any combination thereof.

Equally, inversion may occur without any method of wall stabilitycontrol being applied, as by example only when inversion is undertakenmanually.

Referring to FIG. 12, a final phase of the fourth inversion step ofFIGS. 9 through 11 is depicted in three-dimensional cross-section viewaccording to any preferred embodiment of the present invention.

According to any preferred embodiment of the present invention,inversion has been completed when the at least one profiled inversionpiston 36 has reached its final design position in a longitudinaldirection 63. At this point:

-   -   The at least one interior flexible surface support structure 44        may be retracted 58 and the spring-tensioner plate 56 may be        moved such that it once again springly compresses the interior        flexible surface support structure 44, or    -   Prior to this retraction, the at least one interior flexible        surface support structure 44 may remain engaged and the at least        one profiled inversion piston 36 may continue to move further in        a longitudinal direction 63 such that any inverted wall or walls        may be stretchingly lengthened (not depicted).

To end the fourth inversion step:

-   -   At any point any above atmospheric pressure 62 may be        disengaged,    -   At any point any below atmospheric pressure source (not        depicted) may be disengaged,    -   The at least one profiled inversion piston 36 may be retracted        back to its home position (not depicted).

As a result of the combination of the mechanical stretch-phase prior tothe blow-phase having an LS substantially greater than 1, the tubularblank having an RSmax substantially 3 or less, at least onedual-container shaped mould cavity set and the profiled piston(s), anintegral double-walled container 68 may be formed as a single bodysuitable for mass-production, with the structure of a first container 69and integrally connected 70 and at least substantially inverted secondsmaller container 71, and whereby the first container 69 and invertedsecond smaller container 71 extend in the same direction as each otherthereby forming an open or at least partially sealed air gap 72 betweenthem.

Additional production steps may be added at any sequence point,including but not limited to:

-   -   Cutting away any part or parts of either integrally connected        container and/or the tubular blank by any method and for any        reason,    -   Converting any partially enclosed bottom wall into a fully        enclosed bottom wall by any method, and may result in a fully        enclosed air gap being formed,    -   Further inverting any features or wall sections in either        integrally connected container by any method, and for any reason        and may result in a partially or fully enclosed air gap being        formed,    -   Adding an additional part or parts of any shape or form to        either integrally connected container by any method and for any        reason, and may result in a partially or fully enclosed air gap        being formed,    -   Adding additional material or materials of any form, property or        nature into the air gap by any method and for any reason        including heat-insulation improvement,    -   The application of additional shaping/forming methods to ensure        that the inverted second smaller container fully assumes its        final design shape/form,    -   Printing onto any surface of either integrally connected        container by any method.

In situations where mass production speeds are not required, a secondsmaller container may instead be manually inverted.

Referring to FIG. 13, an open thermoplastic resin tubular blank isdepicted in three-dimensional cross-section view according to a secondpreferred embodiment of the present invention.

According to the second preferred embodiment of the present invention,an open tubular blank 73 may have a first open end 74 and a second openend 75, and may be optimised by design such that its RSmax issubstantially 3 or less in order to minimise the wall thickness 76 ofthe open tubular blank 73 as well as to minimise the wall thickness ofthe integral double-walled container to be stretch-blow moulded (notdepicted).

As heat-conditioned tubular blanks are stretched by mechanical and/orgas pressure in order to stretchingly conform them to dual-containershaped mould cavity sets, at one or more locations tubular blanks mustbe;

-   -   Mechanically clamped sufficiently to enable them to be        stretched, and    -   Sealingly clamped sufficiently such that pressure may be applied        into their interior.

It is typical that the open ends 74 and 75 of an open tubular blank 73be substantially round (as depicted) as this provides the most secureand efficient manner of mechanical and sealing attachment. However,other than at the open ends 74 and 75, the circumferential shape 77 maybe any combination of geometric and/or non-geometric forms, or anychange(s) in circumference, as intended by design and relative totubular blank expansion according to the final double-walled containershape to be formed.

For an open tubular blank 73, mechanical clamping may be effected atboth ends 74 and 75. Mechanical clamping may be in the form of one ormore integral mechanical clamping features 78 at either/or both openends which engagingly interconnect with external mechanical vice orclamp style arrangements in a dual-container shaped mould cavityarrangement (not depicted). There may also be no clamping features 79 ateither/or both open ends.

For an open tubular blank 73, sealing damping may also be effected ateither/or both open ends in order for gas pressure to have at least asubstantially sealed pathway 5 into its interior and which engaginglyinterconnects with external sealing style arrangements in adual-container shaped mould cavity arrangement (not depicted). Sealingdamping is typically incorporated as part of mechanical damping, and mayinclude any combination of common and/or additional integral features inorder to assist with sealing.

The preferred thermoplastic resin for an open tubular blank 73 ispolypropylene (PP), however any suitable thermoplastic resin may equallybe used. A thermoplastic resin may be oil based or bio-based,clear/transparent, semi-transparent or opaque, of its natural resincolour or of any colour or combination of colours, of a single resintype or of a combination of resin types, or any combination thereof.

Referring to FIG. 14, at least part of a first dual-container shapedmould cavity arrangement is depicted in three-dimensional view accordingto the same second preferred embodiment of the present invention.

According to the second preferred embodiment of the present invention,at least part of a first dual-container shaped mould cavity arrangement80 typically includes, but is not limited to:

-   -   At least part of a first dual-container shaped mould cavity set        81 with integral and interconnected cavity recesses that include        but are by no means limited to:    -   A large-aperture recess for mechanical and/or sealing        engaging-connection 82 that may connect to at least one open end        of an open tubular blank 73,    -   An engagingly connected first container cavity recess 83        including a mouth opening zone 84, side wall zone(s) 85 and a        partially enclosed bottom wall zone 86 that may all include        small-radius cavity wall features for any purpose,    -   An engagingly connected second smaller container cavity recess        87 including a mouth opening zone 88, side wall zone(s) 89 and a        partially enclosed bottom wall zone 90 that may all include        small-radius cavity wall features for any purpose,    -   With the first 83 and second smaller container 87 cavity        recesses extending in opposite directions from each other and        integrally connected 91, and    -   An arrangement for assisting with the mechanical stretching an        open tubular blank 73 that has two open ends, as depicted in the        form of an arrangement 92 that may sealingly and/or mechanically        engage with at least one open end 93 of an open tubular blank 73        by any known method in order to assist with the mechanical        stretching of a heat-conditioned open tubular blank in a        longitudinal axis direction 94.

The process steps for forming an integral double-walled container mayoccur as in-line process steps, as adjacent process steps, or as remoteprocess steps, or any combination thereof. It is preferred that theprocess steps occur in-line and/or adjacent to each other.

Each process step and apparatus device as taught may occur once only ina production sequence in any order, or any one or more process stepsand/or apparatus device may occur multiple times, ether sequentially ofnon-sequentially as required in order to achieve the most efficientoverall production throughput. Any one or more process steps as taughtherein may be combined together or separated into sub-steps as required.

Where reference has been made to methods and/or apparatus as part of theformation of a stretch-blow moulded double-walled container with thestructure of two integrally connected and adjacent containers extendingin the same direction as each other and with an air gap between them andformed as a single body from a tubular blank with only one open end,they may equally be part of the methods and/or apparatus in theformation of a stretch-blow moulded double-walled container with thestructure of two integrally connected and adjacent containers extendingin the same direction as each other with an air gap between them andformed as a single body from a tubular blank with a first and secondopen end, and vice versa.

Where reference has been made to a method and apparatus that at leastsubstantially inverts the second smaller container and does not invertthe first container, equally a method and apparatus may at leastsubstantially invert the first container and may not invert the secondsmaller container.

Where reference has been made to a method and apparatus whereincontainer inversion is as a result of mechanical devices, equally amethod and apparatus may include one or more manual container inversionsteps.

Referring to FIG. 15, alternate dual-container shaped mould cavityconfigurations are depicted in three-dimensional view according to anypreferred embodiment of the present invention.

According to any preferred embodiment of the present invention, a secondsmaller container cavity recess may be slightly smaller than itsrespective first container cavity recess, or a second smaller containercavity recess may be substantially smaller than its respective firstcontainer cavity recess (not depicted).

A second smaller container cavity recess may have substantially the sameshape/form 95 as its respective first container cavity recess, or asecond smaller container cavity recess may have a substantiallydifferent or totally different shape/form 96 to its respective firstcontainer cavity recess. The mould cavity set halves in acontainer-shaped mould cavity set may be exact mirror image copies ofeach other, or the mould cavity halves in a container-shaped mouldcavity set may be of different cavity shapes/forms to each other (notdepicted).

The prime market applications for integral double-walled containersformed as a result of the method and apparatus herein taught include,but are not limited to:

-   -   As a cup for fast food and coffee retail outlets, as by example        only as already depicted in the dual-container shaped mould        cavity configurations of previous Figs.,    -   As a plate or lid for fast food and coffee retail outlets, as by        example only as depicted in the dual-container shaped mould        cavity configuration 97,    -   As a bottle or pottle for perishable foodstuffs,        pharmaceuticals, chemicals and cosmetics, as by example only as        depicted in the dual-container shaped mould cavity        configurations 98 and 99,    -   As a container for fast foods, as by example only as depicted in        the dual-container shaped mould cavity configuration 100,    -   As a secondary packaging cup, glass, bottle, plate, lid or        container for any market sector, as by example only as depicted        in the dual-container shaped mould cavity configurations 97, 98,        99 and 100.

Where reference has been made to a method and apparatus wherein thesecond container is smaller than the first container, equally a methodand apparatus may have a first container that is smaller than the secondcontainer.

Where in the foregoing description reference has been made to integersor components having known equivalents, then such equivalents are hereinincorporated as if individually set forth.

Although this invention has been described by way of example and withreference to possible embodiments thereof, it is to be appreciated thatimprovements and/or modifications may be made thereto without departingfrom the scope or spirit of the invention. Any one or more elements thatcomprise any embodiment may equally be combined in any order intofurther embodiments readily apparent to those versed in the art.

1. A method for producing a double-walled container with the structureof two integrally connected and adjacent containers extending in thesame direction with an air gap between them, the method comprising thesteps of: providing a first mould with a first mould cavity having adual-container shape; providing a below melt-temperature thermoplastictubular blank with an open first end and an opposite second end, theblank having an initial blank length L0 and an Smax lower than 3, whereRSmax is herein defined as the largest value of RS occurring along thelength of the tubular blank and Radial Stretch ratio RS is hereindefined as the ratio between a circumference at any point after pressurestretching and the corresponding circumference of the original tubularblank; heat-conditioning the tubular blank to a first heat-conditionedtemperature within a heat softened temperature range but below the melttemperature of the thermoplastic material; placing the heat-conditionedtubular blank inside the first dual-container shaped mould cavity;applying a mechanical blank stretcher to mechanically stretch theheat-conditioned tubular blank in a longitudinal axis direction to astretched length L1, such that the Longitudinal Stretch ratio LS, hereindefined as the ratio L1/L0, is larger than 1; blow-forming thelongitudinally stretched tubular blank outwards by gas pressure in orderto conform the longitudinally stretched tubular blank to the first mouldcavity such that the maximal stretch-blow mould ratio RLmax, hereindefined as the ratio between RSmax and LS, is lower than 3 andpreferably substantially 1 or less; to obtain as an intermediate producta stretch-blow moulded integral dual-container with the structure of afirst container and integrally connected second container, with thefirst container and second container extending in opposite directionsfrom each other, wherein said second end of the tubular blank forms abottom portion of the second container; and then: inverting the secondcontainer such that it extends in the same direction as the firstcontainer; to obtain as an end product a stretch-blow moulded integraldouble-walled container with the structure of a first container andintegrally connected second container extending in the same directionwith an air gap between the first container and second container.
 2. Themethod according to claim 1, further comprising, before the step ofinverting the second container, the step of: heat-conditioning thestretch-blow moulded integral dual-container in any relevant region orregions of the first container and/or second container to a secondheat-conditioned temperature; wherein the step of inverting the secondcontainer is executed while the stretch-blow moulded integraldual-container is in a heat-conditioned state.
 3. The method accordingto claim 1, further comprising the steps of: providing a second mouldwith a second mould cavity having a dual-container shape; placing thestretch-blow moulded integral dual-container inside the seconddual-container shaped mould cavity; wherein the step of inverting thesecond container is executed while the stretch-blow moulded integraldual-container is inside the second dual-container shaped mould cavity.4. The method according to claim 1, wherein the step ofheat-conditioning the stretch-blow moulded integral dual-container isexecuted either prior to insertion into the second dual-container shapedmould cavity, while inside the second dual-container shaped mouldcavity, or both.
 5. The method according to claim 1, further comprisingthe step of manually inverting the second container.
 6. The methodaccording to claim 1, wherein said second end of the tubular blank isclosed.
 7. The method according to claim 1, wherein said second end ofthe tubular blank is open.
 8. The method according to claim 1, whereinthe step of inverting the heat-conditioned second container is performedby: providing at least one profiled inversion piston capable of beingdisplaced in the longitudinal direction of the second dual-containershaped mould cavity; engaging the at least partial bottom wall of theheat-conditioned second container with the at least one profiledinversion piston; displacing the at least one profiled inversion pistonin the longitudinal direction of the second dual-container shaped mouldcavity such as to displace the at least partial bottom wall of theheat-conditioned second container towards and into the first container,wherein a side wall of the heat-conditioned second container is invertedprogressively with progression of the displacement of the bottom wall ofthe heat-conditioned second container.
 9. The method according to claim1, further comprising the step of stabilising a side wall of the firstcontainer and/or second container during the step of inverting thesecond container.
 10. The method according to claim 9, wherein the stepof stabilising a side wall of the first container and/or secondcontainer comprises the step of applying higher than atmospheric airpressure interior to at least one integrally connected pressure chamberand/or the dual-container mould cavity in order to provide a higher thanatmospheric air pressure interior to the stretch-blow moulded integraldual-container during inversion.
 11. The method according to claim 9,wherein the step of stabilising a side wall of the first containerand/or second container comprises the step of applying lower thanatmospheric air pressure via the dual-container mould cavity to any oneor more exterior surfaces of the stretch-blow moulded integraldual-container in the region or regions where wall stability control isrequired.
 12. The method according to claim 9, wherein the step ofstabilising at least one of a side wall of the first container and asecond container comprises the step of inserting at least one flexiblewall surface support member into the second dual-container mould cavityand making the at least one flexible wall surface support member contacta relevant region or regions of interior surfaces of the stretch-blowmoulded integral dual-container.
 13. The method according to claim 9,wherein said relevant surface legion is the connection region betweenmouth opening zones of the first container and second container.
 14. Themethod according to claim 9, wherein at least one flexible wall surfacesupport member has a head-shape so shaped/formed in order to assist withthe formation of the final inversion shape/form desired at the point ofintersection of inverting and non-inverting walls.
 15. The methodaccording to claim 8, wherein at least one of said inversion pistons hasa flat pushing face.
 16. the method according to claim 8, wherein atleast one of said inversion pistons has a fully profiled face thatconforms to the final shape of the interior surface of the at leastpartial bottom wall of the second container to counteract inversion ofthe bottom wall of the second smaller.
 17. The method according to claim12, wherein during the step of inverting the at least one flexible wallsurface support member and at least one of said profiled inversionpistons cooperate to stretchingly extend wall length of the invertedsecond container.
 18. The method according to claim 1, furthercomprising, at any point in the production sequence, the additional stepof cutting away one or more portions of the first container and/or oneor more portions of the second container and/or one or more portions ofthe tubular blank.
 19. The method according to claim 1, furthercomprising, at any point in the production sequence, the additional stepof converting any one or more partially enclosed bottom walls into fullyenclosed bottom walls.
 20. The method according to claim 19, wherein thestep of converting a partially enclosed bottom wall into a fullyenclosed bottom wall comprises the step of forming a partially or fullyenclosed air gap.
 21. The method according to claim 1, furthercomprising, at any point in the production sequence, the additional stepof further inverting any features or wall sections in either integrallyconnected container.
 22. The method according to claim 21, wherein thestep of further inverting any features or wall sections in eitherintegrally connected container comprises the step of forming a partiallyor fully enclosed air gap.
 23. The method according to claim 1, furthercomprising, at any point in the production sequence, the additional stepof adding an additional part or parts of any shape or form to eitherintegrally connected container.
 24. The method according to claim 23,wherein the step of adding an additional part or parts of any shape orform to either integrally connected container comprises the step offorming a partially or fully enclosed air gap.
 25. The method accordingto claim 1, further comprising, at any point in the production sequence,the additional step of adding additional material or materials of anyform, property or nature into the air gap.
 26. The method according toclaim 1, further comprising, at any point in the production sequence,the additional step of applying additional shaping/forming methods toensure that the inverted container fully assumes its final designshape/form.
 27. The method according to claim 1, wherein the resultingdouble-walled container has a highly uniform average wall thicknesssignificantly less than 0.35 mm, and preferably between 0.10 mm and 0.30mm.
 28. A stretch-blow moulding apparatus for producing a mechanicallyinverted double-walled container with the structure of two integrallyconnected and adjacent containers extending in the same direction withan air gap between them, the apparatus comprising: a first mould with afirst mould cavity having a dual-container shape, designed for receivinga thermoplastic tubular blank with an open first end and an oppositesecond end, said cavity including a large-aperture recess for mechanicaland/or sealing engaging-connection to the open end of the tubular blank,an engagingly connected first container cavity recess which includes amouth opening zone, side wall zone(s) and a partially enclosed bottomwall zone, an engagingly connected second container cavity recessincluding a mouth opening zone, side wall zone(s) and a partiallyenclosed or fully enclosed bottom wall zone, with the first and secondcontainer cavity recesses extending in opposite directions from eachother; a second mould with a second mould cavity having a dual containershape, designed for receiving said stretch-blow moulded integraldual-container, said second cavity including a large-aperture, recessfor mechanical and/or sealing engaging-connection to the partiallyenclosed bottom wall of said stretch-blow moulded first container, anengagingly connected first container cavity recess including a mouthopening zone, side wall zone(s) and a partially enclosed bottom wallzone, an engagingly connected second container cavity recess including amouth opening zone, side wall zone(s) and a partially enclosed bottomwall zone, with the first and second container cavity recesses extendingin opposite directions from each other, and at least one engaginglyconnected profiled inversion piston recess as part of the bottom wall ofthe second container cavity recess, and optionally including at leastone heat-conditioning device for heating the first container or secondcontainer or both of the said stretch-blow moulded integraldual-container, and optionally including at least one pathway forinterconnection with at least one below atmospheric air pressure source;at least one profiled piston; at least one wall stability device; and amechanical blank stretcher for mechanically stretching the tubular blankin a longitudinal axis direction when in a heat-conditioned condition;the apparatus being adapted to perform the method of claim
 1. 29. Astretch-blow moulding apparatus for producing a manually inverteddouble-walled container with the structure of two integrally connectedand adjacent containers extending in the same direction with an air gapbetween them the apparatus comprising: a first mould with a first mouldcavity having a dual-container shape, designed for receiving athermoplastic tubular blank with an open first end and an oppositesecond end, said cavity including a large aperture recess for mechanicaland/or sealing engaging-connection to the open end of the tubular blank,an engagingly connected first container cavity recess which includes amouth opening zone, side wall zone(s) and a partially enclosed bottomwall zone, an engagingly connected second container cavity recessincluding a mouth opening zone, side wall zone(s) and a partiallyenclosed or fully enclosed bottom wall zone, with the first and secondcontainer cavity recesses extending in opposite directions from eachother; a mechanical blank stretcher for mechanically stretching thetubular blank in a longitudinal axis direction when in aheat-conditioned condition; and may have at least one profiled piston;and at least one wall stability device; the apparatus being adapted toperform the method of claim
 1. 30. The method according to claim 1,wherein the mechanical blank stretcher has heat-conditioning.
 31. Themethod according to claim 1, wherein the second container is smallerthan the first container and wherein after inversion the secondcontainer is internal to the first container.
 32. The method accordingto claim 1, wherein the first container is smaller than the secondcontainer and wherein after inversion the first container is internal tothe second container.
 33. The method according to claim 1, wherein thefirst container is inverted and the second container remains at leastsubstantially non-inverted.